Not applicable.
The present invention relates to a method for modulating the activity of one or more enzymes that produce precursors of lipid metabolites associated with gastric inflammation, to reduce the deleterious effects of gastric inflammation and to enhance animal and human growth or improve feeding efficiency.
Enhancing animal growth or feed efficiency, can have substantial impact on, for example, the animal meat industry by reducing the high cost of feeding food-producing animals and directly improving profitability. For example, in the poultry industry, even a slight increase in broiler growth rate coupled with reduced feed consumption brings the broiler to market maturity faster at lower cost. With approximately seven billion broilers raised annually in the United States, significant savings are realized.
Methods are known for controlling feeding behavior by modulating the activity of gut peptides that control gastrointestinal motility. These gut peptides include cholecystokinin (CCK), the avian pancreatic polypeptide (aPP), bombesin, gastrin, somatostatin, and neuropeptide Y. Duke, G. E., xe2x80x9cRecent Studies on Regulation of Gastric Motility in Turkeys,xe2x80x9d World""s Poultry Science Association Invited Lecture, pp. 1-8 (1991); Baile et al., xe2x80x9cHormones and feed intake,xe2x80x9d Proc. Nutr. Soc., 42:113-27 (1983). The effect upon feeding behavior of physiological regulators other than the gut peptides is largely unknown.
One set of such regulators include inflammatory metabolites such as the leukotrienes and the prostaglandins which can have beneficial, as well as damaging, effects on the host.
In animals, linoleic acid is converted to arachidonic acid. Arachidonic acid is released (as arachidonate) from the sin2 position of membrane phospholipids by phospholipase A2 (PLA2) and is converted by lipoxygenase or cyclooxygenase into precursors for biologically active prostaglandins and leukotrienes. Perhaps as a result of artificially high dietary linoleic acid levels, animals can contain high levels of the prostaglandin and leukotriene precursors.
Prostaglandins are C20 fatty acids formed from arachidonic acid by cyclooxygenase activity. Prostaglandins cause inflammatory effects during gastrointestinal traumas, such as colitis and ulcers, and are involved in vasodilation, vasoconstriction, and stimulation of intestinal or bronchial smooth muscle. Prostaglandins are found in inflammatory exudates and can induce fever and erythema. Leukotrienes, which are formed from arachidonic acid in response to immunological or non-immunological leucocytes and macrophages stimulation, cause contraction of smooth muscle, such as intestinal smooth muscle, attract leukocytes and stimulate vascular permeability.
It may be possible to reduce inflammation by reducing gastrointestinal prostaglandin synthesis, perhaps by using selective inhibitors of cyclooxygenase-2, an enzyme expressed at inflammation sites. This would reduce or eliminate the need for standard nonsteroidal anti-inflammatory drugs which are known to have ulcerogenic side effects. However, Reuter et al. have shown that inhibition of cyclooxygenase products, such as prostaglandin, exacerbated colitis and increased inflammation-associated colonic injury. Reuter et al., xe2x80x9cExacerbation of Inflammation-associated Colonic Injury in Rat through Inhibition of Cyclooxygenase-2,xe2x80x9d J. Clin. Invest., 98(9):2976-85 (1996). Likewise, Uribe et al. have shown that using indomethacin to inhibit prostaglandin synthesis causes intestinal ulcers. Uribe et al., xe2x80x9cEndogenous Prostaglandins and Microflora Modulate DNA Synthesis and Neuroendocrine Peptides in the Rat Gastrointestinal Tract,xe2x80x9d Scand. J. Gastro., 32:691-99 (1997). Other research has shown that prostaglandins are necessary for gut function repair. Blikslager et al., xe2x80x9cProstaglandins I2 and E2 Have a Synergistic Role in Rescuing Epithelial Barrier Function in Porcine Ileum,xe2x80x9d J. Clin. Invest., 100(8): 1928-33 (1997).
These findings suggest that downregulating prostaglandin activity would be deleterious to an animal""s gastrointestinal system.
The present invention is summarized in that gastrointestinal inflammation is reduced, resulting in improved gut health, enhanced growth and increased feed efficiency in animals, without deleterious effect, by limiting bioavailability of a leukotriene and prostaglandin precursor.
In a related aspect, the invention is summarized in that the antibody can limit availability of arachidonic acid.
In another aspect of the invention, anti-PLA2 antibodies are administered to an animal to increase growth or improve feed efficiency. The anti-PLA2 antibodies limit availability of arachidonic acid, a precursor to inflammatory lipid metabolites such as leukotrienes and prostaglandins.
In yet another aspect of the invention, anti-PLA2 antibodies are administered to an animal to counteract inflammatory problems involving the gut, whether arising from exposure to endotoxin or infectious agents, or from inflammatory processes such as Crohn""s.
It is an object of this invention to provide a method for reducing gastrointestinal tract inflammation, resulting in improved health, enhanced growth or increased feed efficiency in animals, without deleterious effect, by limiting availability of precursors to prostaglandin and leukotriene metabolites.
It is another object of the present invention to reduce availability of arachidonic acid without detrimental effect on the animal.
Not applicable.
Prostaglandins and leukotrienes are believed to cause gastrointestinal inflammation which increases tissue damage and negatively affects the ability of animals, particularly mammals and avians, to convert feed into body weight. Limiting the availability of the precursors for these lipid metabolites reduces gut wall thickening, alters animal feeding behavior and improves animal health.
When the gut encounters endotoxins, Phospholipase A2 (PLA2) becomes active and an inflammatory response begins which can cause gut wall thickening and decreased weight gain. By limiting the production of lipid metabolites such as prostaglandin and leukotriene during normal food digestion, stimulation of intestinal smooth muscle is reduced, and more efficient feed conversion and bodily growth results. By limiting these lipid metabolites during gastrointestinal traumas, such as colitis and necrosis, inflammation is reduced and further tissue damage is avoided. The invention is preferably practiced on avian or mammalian animals. Preferred avian animals include chickens, ducks, turkeys, quail, and geese. Preferred mammalian animals include bovine, ovine, porcine, caprine, rodent and human animals.
In a preferred embodiment of the present invention, prostaglandin and leukotriene production is limited by decreasing the availability of arachidonate, a necessary precursor, by reducing or preventing arachidonate from being cleared from membrane phospholipids. One method for doing so involves interfering with phospholipase A2 (PLA2), the enzyme that clears arachidonate from membrane phospholipids. By reducing or preventing arachidonate release, the pool of available prostaglandin and leukotriene precursors is necessarily reduced.
The applicant has determined that by reducing the available arachidonate, the levels of prostaglandins and leukotrienes are reduced. The strategy is preferably practiced by preventing arachidonate release. This can be preferably achieved by reducing or eliminating activity of the PLA2 enzyme. The PLA2 enzyme activity can be reduced using an anti-PLA2 antibody which, without intending to limit the applicant, is believed to complex with the PLA2 enzyme and thereby interfere with its phospholipase activity. Polyclonal or monoclonal anti-PLA2 antibodies can be prepared or administered using any of various methods known in the art to produce an antibody or antibody-like factor, including, but not limited to, production in transgenic plants or milk producing animals. Suitable antibodies can be, but need not be purified from non-antibody material present during preparation. Antibodies are considered suitable in the present method if they are able to reduce PLA2 enzyme activity relative to untreated controls in side-by-side in vivo trials.
A skilled artisan can use other methods for reducing PLA2 enzyme activity, such as a method of administering a non-antibody pharmaceutical agent that affects PLA2 activity, in combination with a suitable carrier. One skilled in the art will also appreciate that the method can be practiced by introducing activity-altering changes to the genetic material of animals that encodes the PLA2 enzyme or by interfering with transcription or translation of PLA2. The agent can also limit the availability of a different precursor of prostaglandins or leukotrienes.
The agent can be administered by injection or by oral delivery, and is preferably administered in combination with a suitable carrier of the type commonly used in delivery of pharmaceuticals or nutritional supplements. Injection methods include, but are not limited to, subcutaneous, intraperitoneal, intramuscular, or intravenous injection. Oral administration, which is preferred, can include, but is not limited to, administration in tablet or powder form. Most preferably, the agent is fed directly by mixing with feed or by coating feed particles as described in U.S. Pat. No. 5,725,873, incorporated herein by reference in its entirety.
In a preferred method, antibodies are prepared as follows. A producer animal is immunized with a peptide or protein, such as PLA2, against which antibodies are desired so that the producer animal produces an antibody to said peptide or protein. A substance containing the antibody is obtained from said producer animal. The antibody can be subject to further purification if desired or can be used without further preparation in an animal feed.
The method of Tokoro (U.S. Pat. No. 5,080,895), incorporated herein by reference in its entirety, can be used to produce a preparation of egg-yolk antibodies. Laying hens can be inoculated with PLA2. Preferably, a suitable adjuvant is administered in conjunction with the hen PLA2 inoculation to enhance the immunization. An adjuvant useful for this purpose is a water-in-oil emulsion adjuvant such as complete Freund""s adjuvant. The PLA2 causes the hens to produce anti-PLA2 antibodies which are passively transferred into the egg yolk of eggs laid by the hens.
An egg preparation, e.g., egg yolks or whole eggs, containing the anti-PLA2 antibody can be collected and homogenized to form an emulsion. The resulting emulsion can be dried to form a powder containing the anti-PLA2 antibody. This powder can then be formulated in a manner appropriate to the administration route and then administered to the desired animals using methods known in the art. The preparation is preferably administered orally, most preferably as a supplement to the animal""s diet.